1. Field of the Invention
The present invention relates to a process for manufacturing a mat consisting of glass strands and the product which results therefrom. By glass mat is meant a product formed by glass strands (these being chopped or continuous strands), the constituent filaments of which remain bonded together, thus being distinguished from glass veil formed by the combining of dispersed glass filaments.
2. Description of the Background
When manufacturing a glass strand mat, among the main problems to be solved are the choice of the nature of the binder which will give cohesion to the mat, the form in which the binder will be used and the process which will ensure contact of the binder with the mat.
There are many solutions to these problems.
Thus, the nature of the binder chosen is usually dependent on its chemical compatibility with the resin system which the mat is to reinforce.
The binder may be used equally well in powder, suspension, emulsion or solution form. When the binder is used in a form other than a dry powder, the liquid with which it is combined is more and more often water so as to avoid the difficulties which the use of organic solvents always presents.
The methods of application are also very varied.
Although deposition of the binder in the form of a dry powder avoids the use of a liquid, which it will be necessary subsequently to remove, it is difficult to distribute it uniformly within the mass of the mat. Moreover, the binder grains sometimes remain in the composite reinforced by the mat, giving it an uneven surface finish.
The deposition of a binder in the form of an emulsion or of a solution in water or in an organic solvent gives the mat good cohesion since, usually, it adheres albeit partly to the glass strands. However, this advantage may prove to be less beneficial when the mat has to be combined with a product which it must reinforce, whether this is organic or inorganic. This is because, when the binder remains on the glass strands during this combining phase, it may constitute an obstacle to good wetting of the said strands by the said product. This is especially the case when the mat is to be combined with a resin which is in the form of a dispersion or suspension in water or with a mixture based on cement and water. This results in a decrease in the mechanical properties and in a poor surface finish of the final composite component.